Chemical weapons used for dispersing chemical warfare (CW) agents over a wide target area pose serious threats to both civilian and military personnel throughout the world. CW agents can be classified into four categories: nerve agents, blister agents, choking agents and blood agents. Some examples of CW agents, which are formulated to inflict death or harm to people, include sarin (GB), soman (GD), distilled mustard (HD), cyanogen chloride (CK), and hydrogen cyanide (AC). In the face of such threats, the ability to rapidly detect and identify CW agents becomes critical to initiating an immediate and effective response to minimize casualties. Such detection relies on the use of vapor detection instruments configured to detect CW agents and other such hazardous vapors. To ensure operational effectiveness, these vapor detection instruments, especially those of newly developed systems, must undergo specific procedures for testing and evaluation prior to service and periodically thereafter.
During testing, test fixtures are typically used to deliver vapor streams containing target particles or analyte to the vapor detection instrument under testing. These test fixtures are generally constructed with an open cup design through which the vapor stream is passed. The open cup includes a closed end through which an inlet is connected to a vapor generating apparatus, and an open end located opposite from the closed end. The gas sampling inlet of the vapor detection instrument is positioned in the test fixture's cup through the open end prior to activating the vapor generating apparatus. Once the vapor generating apparatus is activated, the vapor detection instrument is challenged via the test fixture as the vapor stream disseminates into the open cup from the inlet. Samples of the vapor stream can be collected by the vapor detection instrument through the corresponding gas sampling inlet to provide the necessary test readings.
The open cup design of the test fixtures offers a suitable means for delivering a vapor stream challenge to vapor detection instruments. However, this design provides no safeguard against inadvertent release of potentially dangerous target particles or analytes into the atmosphere at large and contamination of the environment or individuals testing the vapor detection instrument. Because portions of the vapor stream not sampled by a typical vapor detection instrument are expelled through the open end of the cup portion of the associated test fixture, the testing must be carried out under a fume hood to capture the expelled vapors, and minimize its release into the testing work area.
The above arrangement provides sufficient safety for non-toxic or slightly toxic target particles or analytes. However, this arrangement is especially impractical where the target particles or analytes are extremely toxic and too dangerous to handle directly. The operation of the test fixtures in fume hoods can pose undue safety hazards to the testing worker. In such circumstances, the test must be performed with the entire assembly (i.e., vapor generating equipment, reference detector, and vapor detection instrument) inside a glovebox under a fume hood. There are several disadvantages associated with above-mentioned test fixtures and their reliance on fume hoods and/or gloveboxes.
Fume hoods alone provide only limited protection against exposure. In addition to their limited protection, the relatively large size and complexity of such equipment necessitates costly and labor intensive cleanup after multiple testing. With regard to gloveboxes, they are quite expensive to fabricate and use. Although gloveboxes are vastly safer and more effective in isolating the toxic target particles or analytes from the immediate work area, the thick gloves and placement of all the equipment therein, make the testing process more difficult to carry out. Furthermore, the placement of the test equipment including the vapor generating equipment and the vapor detection instrument within the glovebox means that they are exposed to the dangerous chemicals during testing. This necessitates not only cleanup and decontamination of the glovebox interior, but also all the equipment housed therein. Accordingly, extensive labor and cost expenditures are accrued after each use.
Accordingly, there is a need to develop a disseminated vapor capture device configured for challenging a gas sampling apparatus, such as a vapor detection instrument, with a vapor stream containing target particles or analytes in a safe, reliable and cost effective manner. There is a further need for a disseminated vapor capture device capable of disseminating a vapor stream that significantly reduces the risks of a testing worker's exposure to the vapor stream, while offering enhanced portability and convenient operation. There is a further need for a disseminated vapor capture device that is lightweight, compact and relatively inexpensive.